Cutting oils



Patented Feb. 23, 1954 I CUTTING OILS Dayton P. Clark, Jr., Somerville,N. J., assignor to Gulf Research & Development Company, Pittsburgh, Pa.,a corporation of Delaware No Drawing. Application September 29, 1950,Serial No. 187,691

7 Claims. 1 This invention relates to cutting oils and more particularlyto improved petroleum base cutting I oils containing stably dissolvedsulfur.

Mineral oils containing dissolved sulfur are well known and have beenfound useful in the metal cutting arts. In the application of thesecompositions the dissolved sulfur presumably reacts at the hot cuttingedge of the cutting tool with the newly machined bright metal surfacesto form a metal sulfide film thereon. This sulfide film surface iseffective to prevent adherence of the cuttings and the machined piece tothe cutting tool.

However, mineral oils are not good solvents for sulfur, such as flowersof sulfur. The amount soluble varies depending upon the particularmineral oil used and upon the conditions under which the sulfur isdissolved, particularly the temperature of the solution. Dissolvedsulfur may be to a substantial degree precipitated from the commonlyavailable sulfur-containing cutting oils by a drop in temperature, forexample to about the freezing point of water. Such cutting oils, whensubjected to low temperatures while in transit or while in storage, maybe seriously damaged because of this sulfur separation. Cutting oilsexposed to such conditions generally possess less than 0.7 per cent ofelementary sulfur in solution.

It is an object achieved by this invention to provide an improvedcutting oil comprising a mineral oil solution of sulfur which is stableat both high and low temperatures. It is a further object achieved bythis invention to provide an improved cutting oil composition comprisinga stable solution of sulfur in which the dissolved sulfur content isgreater than the normal saturation solubility of sulfur in the mineraloil.

Another object of this invention is to produce a cutting oil containingan additive that increases the solubility of sulfur in the mineral oil.Other objects of this invention will be apparent in the body of thisdisclosure.

I have discovered that when a phosphatide such as lecithin, cephalin, ora mixture of lecithin and cephalin is added to mineral oilhaving an A.S. T. M. aniline point below about 85 6., there occurs a change in theability of the oil to dissolve and hold in solution added amounts offlowers of sulfur. A greater amount of flowers of sulfur is dissolved bythe mineral oil solution containing a phosphatide than can be dissolvedby the mineral oil alone at corresponding temperatures, and thisincreased amount of dissolved sulfur is notprecipitated from the.phosphatidecontaining mineral oil solution even at temperatures as lowas 32 F. A mineral oil characterized by having an A. S. T. M. anilinepoint below about 85 C. and containing as little as about 0.1 per centof a lecithin-cephalin mixture retains the entire amount of sulfur thatis dissolved at temperatures in excess of 250 F. even when held at suchlow temperaturesas 32 F.

By the term phosphatide as used herein and in the appended claims I meanto include the pure phosphatides such as lecithin and cephalin andmixtures of phosphatides such as the commercially available mixtures oflecithin, cephalin, oil, etc.

The lecithins are phosphatides having the general formula:

I CEO-C0111 In this formula, as in -the case of, the lecithin formulaabove, the fatty acid constituents R1 may be saturated or unsaturated,as for example,

stearic, palmitic oleic,'and like components. The similarity of thelecithins and the cephalins is evident in their chemical and physicalcharacteristics. Thus both compounds behave similarly towardmanysolyents; for example, both are soluble in hydrocarbon-oilsbut-insoluble in acetone. .Both are waxy in nature and white when pure.Both are easily oxidized on standing in air. The lecithins and thecephalins possess no melting point as both decompose on heating.

Moreover, the various lecithins and cephalins may occur in an alpha orbeta form, depending upon the location of the phosphate group in thesubstituted glycerine molecule. If the phosphate group is present on anend carbon atom, the compound is given the alpha configuration; whereas,if the phosphate is present on the middle carbon atom, the compositionhas the beta configuration. Lecithins and cephalins, therefore, mayoccur in either the alpha or beta modification and may vary incomposition depending upon the fatty acid tained therein.

I have found that these various lecithins and cephalins and mixtures oflecithins and cephalin's are useful for the purpose of my invention andcan be interchangeably used therein, and when referring to lecithins andcephalins andmixtures of lecithins and cephalins herein and in theappended claims, I mean to include alpha and beta lecithins andcephalins and the lecithins and cephalins containing different fattyacid substituents and mixtures of the various lecithins and the variouscephalins containing minor amounts of other components such as vegetableoils. Many of the commercially available products sold as lecithin arephosphatide mixtures containing lecithin, cephalin and relatively largeamounts of vegetable oils. These mixtures. may be used in my inventionwithout any further purification, but the amount used should be basedupon the total phosphatide content of the prodnot. If one so desires,such lecithin-cephalin mixtures containing varying amounts of vegetableoils may be purified by extracting the vegetable oils present therein bymeans of acetone. Also, separation of the lecithins from the cephalins,if desired, may be efiected by extraction with cold alcohol, since underthis condition the lecithins are the more alcohol-soluble constituents.However, for the purpose of my invention, this separation is notnecessary, since I have found that lecithinand cephalin, beingsubstituents conphosphatides of a similar chemical nature, areaboutequally effective-whether used alone or in admixture in promotingsolution of sulfur in the mineral oil compositions. In carrying out myinvention, satisfactory results have been obtained with thelecithin-cephalin mixtures in their commercially available'form'known as"Gliddol-R (The Glidden Company,'-'Chicago, 111.). Other commerciallecithin-cephalin mixtures are also usable.

The amount of phosphatide incorporated in the cutting oil according tomy invention may be varied substantially. With an amount as low as 0.1per cent by weight of the oil, a substantial increase in thesulfur-dissolving properties of the composition is obtained. Greateramounts of sulfur will dissolve if larger amounts of phosphatide areused. In general, however, it is not necessary to use more than about1.5 per cent of phosphatide to obtain as high an amount of stablydissolved sulfur as is usually required for a cutting oil composition.Higher amounts of phosphatide may be used without deleterious eflect.Particularly good .results are obtained with concentrations ofrab'out0.25 to:1.0 percent of phosphatide by weight; .Withinthese-concentrations the amount. orstably dissolved-sulfur the presenceof phosphatide.

4 may be between about 0.8 and 2.0 per cent at 32 F.

The mineral oils used in the cutting oil compositions of my inventionare those having a viscosity within the range of the common lubricatingoils with those having a viscosity between about 50 and about 300 S. U.S. at F. being particularly advantageous. My invention is applicable tomineral oils having an A. S. T. M. aniline point below about 85 C.Mineral oils having an aniline point substantially above 85 C., such asmineral white oil having an aniline point of about C., are not improvedwith respect to their sulfur-dissolving properties by An oil having aviscosity of about 100 S. U. S. at 100 F. and an aniline point of about75 C. has produced particularly good cutting oil compositions.

In preparing a cutting oil in accordance with my invention, I prefer tomix the mineral oil, the desired amount of sulfur, and the phosphatidein a suitable mixing kettle with heating. Heat is then applied to thecontents until a final temperature above the melting point of sulfur isattained. The final temperaure is ordinarily between about 250 and 350F. The most advantageous temperatures are those of about 280 F. orhigher. But the lower temperatures, though less satisfactory becausethey prolong the time required for the complete solution of the sulfur,are nevertheless operable.

As an example of my invention I have compounded a cutting oil from 1part flowers of sulfur, 0.50 part by weight of Gliddol-R, the lattercontaining at least about 50 per cent by weight of a mixture oflecithin-cephalin, and 98.50 parts by weight of a 100/2 Texas oil havinga viscosity of 104 S. U. S. at 100 F. and an A. S. T. M. aniline pointof 742 C. The oil containing the lecithin-cephalin mixture was digestedwith the sulfur at about 280 F. until all the sulfur had dissolved, aprocess usually requiring not more than about five minutes.

On cooling this composition to 32 F., the mineral oil retained all thesulfur in a stably dissolved state. When, however, the same base oil wasdigested at 280 F. with 1.0 part by weight of flowers of sulfur, butwithout any phosphatide additive, until all this sulfur had dissolved, aportion of this dissolved-sulfur was precipitated when the solution wascooled to 32 F. This cold solution contained but 0.7part by weight ofsulfur. The lecithin-cephalin additive therefore had increased thesulfur content about 0.3 per cent over the amount of sulfur stablydissolved at 32 F. in the mineral oil alone.

In a lathe performance test it was found that the 100/2 Texas oilhavinga viscosity of 104 S. U. S. at 100" F. and an A. S. T. M. anilinepoint of 742 0., when used alone or used in combina-. tion with alecithin-cephalin mixture, only slightly affected the tool life of thecutting tool. In these cases the tool life was increased from 27 minutesobtained with dry cutting to about 35 minutes and 40 minutes,respectively. In a comparative test, the 100/2 Texas oil contain ingabout 0.7 per cent dissolved flowers of sulfur but no lecithin-cephalinmixture gave a tool life of minutes. 0n the other hand, a cutting oilcontaining 98.5 per cent of the 100/2 Texas oil, 0.5 per cent Gliddol-R(about 50 per cent lecithin and 'cephalin content),- and 1.0 per centstably dissolved flowers of sulfur exhibited no sulfur'precipitationeven on long. standing at 32iand gave a tool life of 640 minutes.

The tool life tests made herein were run on 1020 S. A. E. (SocietyAutomotive Engineers) annealed steel using a high-speed steel (18-4-1)tool of standard contour at a feed of 0.016 inch per revolution, a cutdepth of 0.047 inch and at a cutting speed of 200 feet per minute. Theresults of the tests are outlined in the table.

In order to illustrate the importance of employing a mineral oil havingan aniline point below about 85 C., sulfur-containing compositions wereprepared from a mineral white oil having a viscosity of 204 S. U. S. at100 F. and an A. S. T. M. aniline point of l08.5 C. When this oil wasdigested at 280 F. with 1 per cent by weight of flowers of sulfur, thesulfur readily dissolved, but

upon cooling the resulting solution to 32 F. needle-like crystals wereprecipitated. When the experiment was repeated using 0.2 per cent ofGliddol-R, needle-like crystals still precipitated on cooling to 32 F.Even when 1.0 per cent of Gliddol-R was employed, the formation ofcrystals on cooling the solution to 32 F. was not prevented.

This application is a continuation-in-part of my co-pending application,Serial No. 677,535, filed on June 18, 1946, now abandoned.

Having discussed my invention with reference to particular embodiments,it is to be understood that these embodiments are merely by way ofillustration and are not limitations of my invention except ashereinafter defined in the appended claims.

1. A petroleum base cutting oil composition consisting essentially of astable solution of flowers of sulfur and a phosphatide in a mineral oilhaving an aniline point below about 85 C., said solution containing agreater amount of dissolved sulfur than can be dissolved in the mineraloil in the absence of said phosphatide.

2. A petroleum base cutting oil composition consisting essentially of astable solution of flowers of sulfur and lecithin in a mineral oilhaving an aniline point below about 85 C., said solution containing agreater amount of dis--.

6 solved sulfur than can be dissolved in the mineral oil in the absenceof said lecithin.

3. A petroleum base cutting oil composition consisting essentially of astable solution of flowers of sulfur and cephalin in a mineral oilhaving an aniline point below about C., said solution containing agreater amount of dissolved sulfur than can be dissolved in the mineraloil in the absence of said cephalin.

4. A petroleum base cutting oil composition consisting essentially of astable solution of flowers of sulfur and a mixture of lecithin andcephalin in a mineral oil having an aniline point below about 85 C.,said solution containing a greater amount of dissolved sulfur than canbe dissolved in the mineral oil in the absence of said mixture oflecithin and cephalin.

5. A petroleum base cutting oil composition consisting essentially of astable solution of about 0.8 to about 2.0 per cent by Weight of flowersof sulfur and about 0.1 to about 1.5 per cent by weight of a, mixture oflecithin and cephalin in a mineral oil having an aniline point belowabout 85 C.

6. The method of preparing a petroleum base cutting oil containingflowers of sulfur stably dissolved therein which comprises heating atbetween about 250 and about 350 F. a mixture consisting essentially of amajor amount of mineral oil having an aniline point below about 85 0.,about 0.8 to about 2.0 per cent by weight of flowers of sulfur and about0.1 to about 1.5 per cent by weight of a phosphatide for a period ofminutes suflicient to effect complete solution of the sulfur andinsufficient to effect sulfurization of said mineral oil.

7. The method of preparing a petroleum base cutting oil containingflowers of sulfur stably dissolved therein which comprises heating atabout 280 F. a mixture consisting essentially of a major amount ofmineral oil having an aniline point below about 85 C., and about 0.8 toabout 2.0 per cent by weight of flowers of sulfur and about 0.1 to about1.5 per cent by of a mixture of lecithin and cephalin for a period ofminutes sufficient to effect complete solution of the sulfur andinsufilcient to effect sulfurization of said mineral oil.

DAYTON P. CLARK, JR.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,138,546 High Nov. 29, 1938 2,159,908 Nill May 23, 19392,339,371 Becker Jan. 18, 1944 2,396,345 Rogers et al. Mar. 12, 1946

1. A PETROLEUM BASE CUTTING OIL COMPOSITION CONSISTING ESSENTIALLY OF ASTABLE SOLUTION OF FLOWERS OF SULFUR AND A PHOSPHATIDE IN A MINERAL OILHAVING AN ANILINE POINT BELOW ABOUT 85* C., SAID SOLUTION CONTAINING AGREATER AMOUNT OF DISSOLVED SULFUR THAN CAN BE DISSOLVED IN THE MINERALOIL IN THE ABSENCE OF SAID PHOSPHATIDE.